Hello everyone. I have pretreated orchid seed with a sugar solution in an attempt to 'wake up' dormant contaminants
prior to sterilization. Has anyone tried this with slippers? I found the technique on the OSP web site and used it with Dend.
seed. Basically, the principle is that active organisms are more susceptible to sterilization than dormant spores etc.


Greg.

Hello everyone. I have pretreated orchid seed with a sugar solution in an attempt to 'wake up' dormant contaminants
prior to sterilization. Has anyone tried this with slippers? I found the technique on the OSP web site and used it with Dend.
seed. Basically, the principle is that active organisms are more susceptible to sterilization than dormant spores etc.


Greg.

This technique is derived from tyndallisation, but tyndallisation implies some heat, which would kill the seeds. Theoretically, 3 or 4 passages of a few hours in the sugar solution, followed by a rinse with sterile water, at a 3-4 day interval, would lead to sterility... Theoretically. Practically it is extremely difficult to avoid any new contamination while so doing.

But what is the advantage of such a practice, since you intend to sterilize all the same ? Dendrobium seed are not particular as to sterilization ?

>>>Chun

Hi. The method involves a 16-24 hour soak(no heat) in a sucrose solution at room temperature. The solution is removed by absorption, optional rinse. The seed is then sterilized and flasked. Please check the OSP site(technical data section) for details. I was only curious if anyone else had used the method. A friend in Rochester who flasks uses this method routinely with all her flasking. There are no issues with sterility or increased contamination. The idea is that vegitative or actively growing bacteria/fungus are more easily destroyed than dormant spores.


Greg.

Sucrose solution treatment overnight prior to regular sterilization for dry seed is commonly used. It does cut down on dormant spores that give you trouble after a few weeks of culture. It is especially good for seed that has been stored for more than a few days of the capsule ripening. I only use it when I am concerned about the seed or have had problems with a previous batch of the same seed.
Dean Stock

Thanks for the info. My flasking has been with dry seed only. I have only used the method on 'old' seed from friends.
Thank you again for your input.


Greg.

I soak all my phrag seed in a sugar solition before sterilzation.

For Cypripediums either the use of a sugar solution or pulling a vacuum decreases contamination and dramatically increases germination. Cypripedium seed when mature has a large air bubble (look with a magnifying glass at floating seed) which causes the seed to float (an annoyance) and apparently it keeps the bleach from reaching the interior of the seed to destroy germination inhibitory chemicals or whatever the evil humours are. I am told that it also decreases contamination. Getting rid of the bubble - sugar does reasonably well, presumably by causing the seed to swell by taking on water, and pulling a weak vacuum does even better. Suspend the seed in a test tube of bleach solution then insert a rubber stopper with tubing attached to a small hand vacuum pump (ebay always has a large number of these for roughly $20, they last forever). Pump to maximum vacuum and leave for about one minute then release the vacuum and allow to sit for a minute. For Cypripedium seed you will probably need three to four cycles of this to get all the seed to sink. For some of the more difficult to germinate species, I have found this treatment to dramatically increase germination compared to the same bleaching without vacuum, in some species from less than 10% to greater than 50%. Like sugar treatment, you will see the embryos swell very dramatically - but within just a couple of minutes since pulling the air bubble out seems to increase permeability to water.

Most other genera I have tried so not seem to have much of an air bubble problem and do not float, but I have found in some that pulling a vacuum also enhances germination percentage (but not a lot since the other genera I have examined have very high germination percentage with no treatment).

Ron

Ron, have you tried this vacuum method with Cyp. calceolus with any success? I have some mature seeds, and I have never had any success with calceolus before. I have sown from green pod as well this year, but yesterday I got 3-4 mature seed capsules.
I will try to get a hand vacuum pump at ebay.

I have tibeticum seeds as well, do you have any advices of bleaching times for tibeticum?